Conversion of hydrocarbon oils



June 24, 1941. 1.. c. HUFF CONVERSION OF HYDROOARBON GEES Original FiledJuly 5, 1935.

muZmUum INVENTOR LYMAN c. HUFF TORNEY Patented June 24, 1941 CONVERSIONOFHYDROCARBON OILS BymamGUHuff', Ghicago, Ill., assignor to UniversalQihProduots- Company; Ghicagm Ill., acorporationcofwn'elaware-ApplicationJuly 5; 1935; Serial No. 29;? 9'5 Renewed April -18; 1939-The present invention refers to an improved process forthe pyrol'yticconversion of relatively heavy-- petroleum-oils; such as topped crudesand the 1 like; at elevated temperature and superat m'ospheric pressurefor the produ'ctionmr high yields of"good" quality"motor fiiel andeithei mai to thekexc'essive frmation an in the heating coil.

spect' to: suspended carbonaceous material and:- the presence ofexcessivea-mounts -of carbona'ceous material in the cracked residue the"present process becomes particularly adaptableto the treatment of toppedcrudes or residual oils of ian iasphaltichatu-re for the production ofcan goodiqua'lity motor fuel -a'nd good quality asphalt although theinvention-ismot limited to thetreatment' of: asplialtici charging toek'snor to the pro c'luct'ion of asphaltl' aathefihal residual"productofthe-process;

In one embodiment? the" invention comprises subjectingresidual'petroleum-fractions of an as phalticr nature to conversion conditions ofcracking: temperature andsubstantial supera-tmospheric" pressure ineommingled state with lowboiling 'normally gaseous hydrocarbons absorbedby contactingthe charging stock} 1 withtheprocess gases," introducingtheresulting heated and partially converted materials into" an enlargedreaction chamberalso i maintaihed at superatmos ph'eric pressure-'wherein the desired conversion reaction are completed} withdrawing bothVa porous" and liquid conversion" products" from the reactionchamber-and introducingthe saine into a reduced pressure vaporizingchamber" wherein separation of vapomus and residiial liquidconversionproduc'ts' is accomplished, withdrawingthewlatter from the"vaporizing chamberand subl jecting the sanieto furtherwdiis'ti'llationat sub atmospheric pressure for theproduction of asphalt, separatelywithdrawingvaporous conversion pro ducts 'from the vaporiairigphamber;subjecting the same to fractionation for the forma tionof'reflux"condensatecomprisingtheirinsufficiently" converted componentsand' the recovery of" fractionated vapors-within of motor fuel, whichlatter-alected; returningtl'ie' refiux condensate to" time pendentlycontrolled conversion conditions" of higher cracking temperature andsuperat'mos pheric pressure in a-separate heating coil; introclucing theheated products from said separate heating coil into thevaporizin'gchamber, subjecting said motor fuel productresultingfrom condensation ofthe fractionated vapors-to stabilization for the removaltherefromofundesirablelow-boiling components; whereby to control its vaporpressure, and contacting the uncondensed gaseous products of theprocess-with said-chargingstock prior to its introduction into=the firstmentioned heating coil.

While the elements of plants for accomplishing the above objectsmay-vary somewhat in their absolute and relative proportionsdepending-upon the character of oil to be-processed andthedesiredresults, the essential features ofoperation comprised in'thescope ofthe present invention are generallysimilar in all' plant's andthe attached drawinghasheeh providedtb assist in describing acharacteristicoperation: The-drawing shows-diagrammatically, by'the useofconventional figures in side elevation, anarra-ngement ofinterconnected elements in which the steps of the processmaybeconducted. Aswill be'shown by a later example; the particularsystemillustrated isparticularly applicable to 'resi'duaI stocks of 1 highspecific gravity;

Referring to the drawing; charging oil is introduced to the plant fromany su'itab le" source of supply, not shown; through a" line Icontaining control valve 2 and isfed byfpurnp 3 through line t and valve5 into a point near thEGOpOf an absorption column 6, from whichtheunabsorbed fiked gases are discharged throughline 'lcontaining controlvalve 8; Theabsorber may be of any conventional typecontaininga seriesof superirnposed bubble trays or other suitable contacting means toinsure substantially complete absorption from the gases-supplied theretoofall hydrocarbons of 4 carbon atoms (the butanes and butylenes) and aportion ofthe propane, while leaving unabsorbed such gases as hydrogen,methane; ethane, ethylene, etc; The' gas mixturesare admitted to theabsorherfromv line 62 as willbe described at a later point Theabsorption of oilvapors'at thispoint having thegeneralcharacteristicsof'the low-boiling fractions of gasoline has atwo-fold advantage in that this material isrecovered to augment theyield of the final light distillate product of the process and that thepresence of appreciable quantities of'such fractions in'theheavychargiing oil has a tendencytolessen coked'eposit'ion in theprimary heating coil, probably due to combination of the low-boilingmaterials with the heavy, coke-forming conversion products. Theconditions employed for cracking the raw oil are hardly severe enough toeffect substantial conversion of the light fractions, which, however, byvirtue of their partial pressure in the heating tubes, serve to makepossible the use of relatively higher temperatures and lower timefactors in this zone.

Raw oil containing absorbed light hydrocarbons passes from the bottom ofabsorber 6 through line 9 and valve Ill to pump H from which it is fedthrough line [2 and valves l3 and I3 to a heating coil comprising tubebanks l4 and [4' within furnace setting 20. Controlled quantities of thecharging stock may be passed through a heat exchanger 29 by way of inletline 21' and valve 28' and outlet line 29' containing valve 30, withvalve l 3 totally or partially closed. This diversion of flow serves toefiect partial preheating of the enriched charging oil from absorber 6and lower the temperature of the vapors from chamber 25, with which itpasses in indirect heat exchange. Obviously, the amount of condensationcaused by the cooling effect of the raw oil will to some extent controlthe quality and end-boiling point of the intermediate fractionsrecovered as reflux condensate in fractionator 34.

The element for heating and instigating cracking reactions in thecharging stock consists, in the case illustrated, of two interconnectedbanks of horizontal tubes l4 and M, respectively, which receiveprincipally radiant heat from combustion gases generated by thecombustion of fuel supplied to combustion and heating zone A of thefurnace by means of suitable burners indicated at is. The combustiongases from heating zone A pass downwardly over a separate bank of tubesI5, within the centrally located fluid heating zone C of the furnace,along with the gases from the other combustion and heating zone B, to bepresently described.

Temperature and pressure conditions employed in the charging stockheating coil may be varied considerably depending on the quality of thecharge but are generally within the limits of 850 to 950 F. and 100 and500 lbs. per square inch.

Heated products are discharged from the charging stock heating coilthrough line 2| containing control valve 22 and pass into a reactionchamber 23, wherein substantial completion of the desired conversionreactions occurs and wherein a substantially superatmospheric pressureis maintained which may be substantially the same or somewhat lower thanthat in the last tubes of the heating element.

In the case here illustrated both vaporous and liquid products aredischarged from the bottom of chamber 23 through line 24 containingpressure control valve 25 and enter a vaporizing chamber 26 maintainedat substantially reduced pressure of the order of 100 lbs. per squareinch to substantially atmospheric pressure, with a reduction intemperature in this zone due to the pressure reduction. In thevaporizing chamber separation of vaporous and liquid conversion productsis accomplished, the former comprising substantially all of the gasolineboiling range fractions and other constituents having characteristicsrendering them suitable for further conversion within the same system.The residual liquid, which is preferably of a fuel oil character at thispoint, is withdrawn through line 93 and a portion or all of it may, whendesired, be cooled and stored for subsequent use after withdrawalthrough line containing control valve 96. When it is desired to furtherreduce this residuum to produce a good grade of marketable asphalt it isfurther subjected to vacuum distillation, which will be described afterthe completion of the description of the cracking process.

The vaporous products from chamber 26 follow vapor line 21 containingcontrol valve 28 and pass through heat exchanger 29 in generalcounter-flow to regulated portions of the charging oil composite, aspreviously described. Line 30 containing control valve 3! indicates adrain line which may be employed for removing heavy material condensedin the heat exchanger. Due to the cooling of the vapors in heatexchanger 29 this zone serves to separate therefrom heavy carbonizableliquids which might cause tube troubles if returned to furtherconversion with the reflux condensate.

The major portion of the vapors supplied to heat exchanger 29, whichremain uncondensed therein, pass from the heat exchanger through line 32and valve 33 to fractionator 34 of the conventional bubble tray varietyor any other suitable form. This fractionator serves to separate thevapors of motor fuel boiling range and fixed gases as an overheadfraction from the higher boiling components of the vapors which arecondensed as reflux condensate. Reflux condensate is withdrawn from thebottom of the tower through a line 75 and valve 16 and pumped by pump Tlthrough line 13, valve 79, line 89 and valve 99 to an independentlyheated tubular cracking element comprising tube banks l5, l6 and H.

In the case here illustrated the heating coil to which the refluxcondensate is supplied is also located within furnace 2i] and thecombustion gases from both combustion and heating zones A and B passover the tubes of bank l5 imparting fluid heat thereto. The roof andfloor tubes l6 and I! are supplied with radiant heat from the materialsundergoing combustion in heating zone B; fuel being supplied to thiszone from a series of burners indicated at [9. The temperature andpressure conditions employed in the reflux heating coil are preferablysomewhat more severe than those employed for the charging stock and maybe of the order of from 900 to 1050 F. and 200 to 800 pounds, or more,per square inch. In the present operation the heated products from thereflux heating coil are directed to the vaporizing chamber 26 by way ofline 9| containing control valve $2., which may join with line 24previously mentioned.

The fractionated vapors and gases from fractionator 34 pass through line35 and valve 36 to condenser 31, from which the resulting distillate anduncondensed gases flow through line 38 and control valve 39 tocollection and separation in receiver 40. In order to effectstabilization of the distillate it is passed from receiver 46 throughline ll and valve 42 to a pump 4-3 from which it is directed throughheat exchanger 4, line 45 and valve 46, recovering heat in the heatexchanger for effecting partial vaporization of the distillate before itpasses into stabilizing column 41.

Column 41 is commonly operated at a pressure of from '75 to 150 pounds,or thereabouts, per square inch, a top temperature of to F. and a bottomtemperature of 250 to 325 F. The function of the stabilizing column Al!is to aeae sea remove all of the. normally gaseousconstituents;including hydrogen; methane; ethane; ethylene,-: propane andpropyleneandaacertairrportiomof! the butanes and butylenes; fromltheldistillatei supplied: to this? zone sou thatfi the. vapor "pressure" of:the: resulting: finishedi gasoline-21s: oftitheleorderr on from 8: to i12-. pounds: per: square: inch: bpthe; Reid-1 test;

When the temperature or the :entering; mates rials afterspassingthroughlheat exchanger Maris notl'higlr enough to:maintainilthe:requireditenra perature: differentialirr the;stabilizingtcoiummair auxiliary heating arrangement. on any? suitable?formzrmay be: employed :f or" reboilings'the r distillate? from thebottom of. column I 41:; Inztheacaser herel illustratedxheat; forreboil'ing 1' is: obtaineda by "the:- diversion of a; portion of" the:reflux: condensate. fromxfractionator" 34; which; QETSSFthITQIIghslinerflm and valve: BII to a closed; coil in: reboi'lenr ;:andi' thencebacktofractionator: 34's eithers directlythrough; line 82, valve: 83and: linerI:I'4 orrbwwayr otcline 84, valve 845; cooler: 86; lineia'lrvaltsejfli an'dHineLIM'. Theiunction'aof coolerillfi'isrtmco trol; thtemperature of x the-s. oil returned: as: res fluxingl liquid: to.fractionator 34r and; thus: assist: in controlling l the 1GhQJaCtEIClOfi the: fractionation. in this zone. Reboiling: ofr thematenia-lstinzlthe bottom1 of thel stabilizing column; is: effected. by;withdrawing thenon-vaporous distillate; from column 4a'I through: line:66 andzvalvefl toereboilen 'Illmfromwhich evolved vapors are returned;torthexcolumncthrough line 68: andya-lve v69"; Stabilized? liquidirepresenting thestabilizedlmotors-fi1elprod:= not of the process iswithdrawn fromlreboilerfilm at a: point remote: from inlet linerfifirthrough lin band valve IZ-and passes through heatilex't changer 44, thefunction or:whichmasrbeenl-pre viously described, after which-:itimaypassto. fur therrcooling and storage onto; any desiredzlfuntheritreatment by way of line 13 containing control: valve-14L The overheadproducts-fromrstabilizing:vcolumni 41: pass" through I line 48?containing controlvalve? 49: and: through a condenser: 50:; which; may;013,- I erate I at i subatmosphericwtemperature if desired; and: theresulting condensategyalong; withtfixedi gases, passes through line 51-containing control valve" 52 to separation in an? accumulation: The":liquid; condensate collected? atntliis-lpointlwillicom prisesprincipally four-carhon atom"-hydrocarhons; with traces of I propane andsome: pertanes; landwif desired a: portion thereof mayrbewithdnawn to rseparate storage a through; line 55 and valve: "55'; The amountnecessary for refluxlng'r at: the? top; of Y the I stabilizing column isewithdrawnvthrouglr line: 5'!" and valve: 58- andTecirculatedibywpump.'59 through "line 60 and valveHI to'columnzk-I: Fixed-l gasescfromreceiver 40 may -passntor absorber: 6w by way of line: I54 and valveand: similarlwgases-i from receiver 54 may I be supplied? tothezsabsorber" through line 02'andvalve 6'3. I

In order to make asphalt froml-thenonsvaporous residualliquidxfromlchamberwzfirpump 91:- supplies all or any desired. portion:thereof" through line 08 and valve 99; to a a-vacuum-Ievapoe rator I00.Using a subatmospheric pressure at this point of the order of from 3 to5 inches or more of mercury absolute pressure enables the efficient andrapid production of marketable asphalts in this zone. The asphalt may bewithdrawn to storage through line IN and a valve I02. Vapors from thevacuum evaporator pass through line IOI and valve I02 to condenser I03and thence the resulting condensate and gas passes through line I04 andvalve I05 to a receiver I00, Thearequisitevacuum is maintainedLimcolumnI00, in the case here illustrated; by withdrawing ,thefixed lgaseslfromlreceiver Il06lthrough line I01 containing control valve I08 toabarometric condenser [09, which maybe or any'con ventional' for-mandtherefore neednot be described imd'etail The overhead distillateproducts from the asphalt evaporation pass through line- H0 and valve III to a pump II2, which" discharges through line" H4. This product will"ordinarily comprise an oill isuitable for example as light domestic orindustrial fuel andaregulated portion or all-ofithis material may bedischarged through branch line H2 and valve 3' to storage orelse whereasdesired and regulated quantities thereof may be used as a refluxing:medium in column I00 to control.thedistillation inthe vacuum evaporatorby passingthe' same through valve I15 in line m: and thence through lineIn containing controLvalve H8. into the upper portion of the evaporator.On the other hand all or any desired portion of the condensate collectedin receiver l'lli may be returned for further conver sibnto--the-1ight-oil heatingcoil of the system.

It may-be supplied direct to-this zone; by' well known means-notillustrated, or mayfirst be utilized'. asa cooling and refluxingmediumtin fractionator 34 by supplying: the same thereto through valveH6 in line II4.

ihg the iollowingproperties-t" ANALYSIS oF'ToPPED CRUDE Gravity; A. P? I1116 Specific gravity" l l 019888 Flash ((Jlevel'and open cup) F; 225*Fire (Clevelandopencup), F 270 Flash (Pensly Martens), Fl .Q. 205Viscosity; fiirol-(il 122 F., sec 1'74 Sulfur-pen cent 4215 I.Coldltest, F 13 BnS:-.&iW.-eper cent--- l 0.3

100*66. distillation I; 13, 12.19 F .-4- l ;..l l l l l 44.1.) 5 5 0530. 646 4.0;- -7. 676- 610 693 eof; r 705" 716 8U.- a l.. 723

Per centzover; 37.5=

" Per-centcokebywt. 12.4 Pen cent"@ *572F 1515' The topped crude whichrepresented 78.3% of the original crude oil was cracked in a plantcorresponding in essential details with the one shown in the drawing toproduce a maximum yield of 375 F. end-point gasoline while proc esslngthe residuum from the flash chamber to produce asphalt of from topenetration. In the following table are summarized the overall resultsof a run which extended over aperiod of several days.

SUMMARY or CRACKING CONDITIONS Temperature at outlet from charging stockheater F' 920 Pressure at outlet from charging stock heater lbs. per sq.in 225 Temperature at outlet from reflux heater F 950 Pressure at outletfrom reflux heater lbs. per sq. in 350 Average temperature inreactionchamber F 870 Pressure in reaction chamber lbs. per sq. in 225Pressure in vaporizing chamber lbs. per sq. in 50 Absolute pressure inasphalt reducing still lbs. per sq. in 1.5

YIELDS, PER CENT BY WEIGHT or CHARGING STOCK Per cent Motor fuel ofapprox. 375 F. end-boiling point 5O Asphalt (80 penetration) 42 Fixedgases 8 PROPERTIES or LIGHT DISTILLATE PRODUCT (UNTREATED GASOLINE)Specific gravity 0.748

Ductility cm 100 Solubility in carbon bisulfide per cent 1 99.3Solubility in carbon tetrachloride do 99.0 Solubility in 86 A. P. I.parafiin naphtha per oent 75 The practical features of the process willbe evident to those conversant with oil refinery operations from thepreceding data on conditions of operation, yields, and the qualities ofthe principal products. However, neither the descriptive material northe numerical data are to be construed as imposing undue limitationsupon the generally broad scope of the invention.

I claim as my invention:

1. In a process for the conversion of hydrocarbon oils whereinintermediate liquid conversion products of the process are subjected toconversion conditions of cracking temperature and superatmosphericpressure in a heating coil and then introduced into a reduced pressurevaporizing chamber wherein vaporous and residual liquid conversionproducts are separated, the vaporous conversion products subjected tofractionation for the formation of reflux condensate comprising saidintermediate liquid conversion products which are supplied to theheating coil for said conversion, fractionated vapors of the desiredend-boiling point subjected to condensation, the resulting distillateand uncondensed gases collected and separated and the distillatesubjected to stabilization whereby to liberate therefrom dissolved gasesand undesirable low-boiling components for the purpose of reducing itsvapor pressure, the improvement which comprises subjecting saiduncondensed gases together with the gaseous products liberated from thedistillate by said stabilization to absorption by contact with chargingstock for the process comprising an oil of higher boilingcharacteristics than said reflux condensate, subjecting charging stockfrom the absorption stage, containing absorbed high-boiling componentsof the gases, to independently controlled conversion conditions ofelevated temperature and superatmospheric pressure in a separate heatingcoil and communicating reaction chamber maintained under higher pressurethan the vaporizing chamber, introducing the resulting conversionproducts from the reaction chamber into said reduced pressure vaporizingchamber, withdrawing residual liquid from said vaporizing chamber,subjecting the same to further distillation at subatmospheric pressurefor the formation of asphaltic residue, recovering the latter,subjecting the vapors evolved by said further distillation of theresidual liquid to condensation and returning resulting condensate tothe fractionating stage of the cracking system.

'2. A conversion process which comprises subjecting a residual petroleumoil to cracking conditions in a cracking zone, simultaneously cracking arecycle stock, formed as hereinafter set forth, at higher temperaturesthan said residual oil in a second cracking zone, discharging thecracked products from both said zones into a reduced pressure vaporizerand therein separating the same into vapors and a liquid residue,fractionating the vapors to condense heavier fractions thereof, removingliquid residue from said vaporizer and reducing the same to an asphalticmaterial by further distillation thereof under subatmospheric pressure,introducing condensate resulting from said further distillation intocontact with said vapors undergoing fractionation as a refluxing mediumfor the vapors, thereby combining said condensate with reflux condensateseparated from the vapors by the fractionation, supplying the resultantcondensate mixture to the second cracking zone as said recycle stock,finally condensing the fractionated vapors and separating the resultantdistillate from normally incondensible gases produced in the process,scrubbing such separated gases with said residual petroleum oil prior tothe introduction of the latter to the first-mentioned cracking zone,whereby to absorb heavier components of the gases in the residual oil,and supplying the absorbed gaseous components to the first-mentionedcracking zone together with said residual oil.

LYMAN C. HUFF.

